As mentioned above, since the invention relates to a treatment of the substrate having the organic dye layer on the surface, in the specification, the intermediate product in this state is simply referred to as a disk and is distinguished from an intermediate product at the other steps and a finished product.
That is, in the specification, it is assumed that the mere word "disk" denotes the intermediate product which has the organic dye layer on the surface of the substrate and none of the reflective layer and the protective layer is formed on the organic dye layer.
In the specification, although the outer peripheral surface of the disk is described to be the cylindrical surface, it is assumed that the cylindrical surface includes a chamfered surface, a surface having rounded corners and the like.
The optical recording disk which is formed by laminating the organic dye layer, reflective layer and protective layer in serial order on to the substrate is disclosed in, for instance, "Optical Data Storage 1989", Technical Digest Series Vol.1 45, 1989, or the like and is well known.
The optical recording disk is widely put into practical use because the information recorded on the disk can be easily reproduced by a compact disc player which is generally commercially available.
When the optical recording disk is manufactured, the organic dye layer is formed on the substrate by a spin coating method, a dipping method, a sputtering method, a vacuum deposition method, or the like. In this case, however, organic materials forming the organic dye layer are undesirably deposited and remain on the cylindrical outer surface of the disk.
When the disk on the cylindrical outer surface of which organic materials are deposited and remain is used to obtain a medium, an appearance of the medium becomes worse, which makes the medium commercially very low value.
When such a disk is handled by fingers of a worker or a chuck of a robot, if the fingers or the chuck comes into contact with the cylindrical outer surface of the disk, the fingers or chuck is polluted by the organic materials, and the deposited materials result in the generation of floating dust.
Further, although the reflective layer and the protective layer are formed on the organic dye layer, the protective layer generally covers a part of or all of the cylindrical outer surface of the substrate. The outermost periphery of the surface of the substrate should have no organic dye layer nor the reflective layer, in order to obtain strong adhesion of the protective layer to the substrate. Further, the organic materials should be removed away from the cylindrical outer surface, thereby allowing the protective layer to be directly adhered onto the clean surface of the substrate. However, if organic materials such as organic dye or the like are deposited and remain on the cylindrical outer surface of the substrate, in such a portion, an adhesion of the protective layer to the substrate becomes poor.
When organic materials such as dye or the like are deposited and remain on the cylindrical outer surface of the substrate as mentioned above, various problems occur. Therefore, the organic materials deposited in such a portion must be completely removed.
Hitherto, we removed away such surplus materials by a manual work by using a cloth with a solvent.
Such a cleaning method, however, provides many problems. For example, much labors and a long time are needed, it is difficult to control the quality, a large amount of floating dust is raised in the work environment, the substrate surface may be damaged during the work, it is harmful from a viewpoint of labor health, and the like.
A method of mechanically cutting and finishing the cylindrical outer surface of such a disk-type substrate has been disclosed in JP-A-4-67333, though the object of the invention is different from that of the present invention.
The organic materials deposited on the cylindrical outer surface of the disk can be also removed by the above cutting and finishing method. According to such a method, however, it is difficult to collect the floating dust generated upon cutting and it is almost impossible to completly remove the generated floating dust.
When such floating dust falls and is deposited onto the organic dye layer formed, further, there occurs serious problems such as defects in the reflective layer or protective layer and in uniformity of of their layers thicknesses.